Surgeons have implemented surgical staplers for many years. In general, there are three main types of linear surgical staplers—open linear staplers, open gastrointestinal anastomosis (i.e., a linear cutter), and endocutters. Staplers are often used in surgical procedures involving the lung, liver, and stomach and are typically used in resection of an organ.
Surgical staplers have some common components. These include a handle, an actuator, and an end effector including a clamping mechanism. The clamping mechanism often has a cartridge and an anvil. For these staplers, the surgeon clamps two members (i.e., the anvil and the cartridge) on the organ and compresses the organ between them. Once compressed, the surgeon uses the stapler to drive or fire staples through the organ. With proper compression and alignment of the clamping mechanism, a B-shaped staple is formed. Some surgical procedures may require multiple staple firings. Each firing often requires the surgeon to reload the stapler with more staples. For example, some staple lines may require 5 to 8 reloads depending on the length and/or the staple capacity of the stapler.
The integrity of a staple line depends on the proper formation of B-shaped staples. This in turn depends on the stapler's capability of compressing tissue while, at the same time, withstanding the forces associated with proper B-shaped staple formation. A B-shaped staple is the standard of care for gastrointestinal, vascular, pulmonary, and hepatic applications of surgical tissue fastening devices. Alignment in each of the X, Y, and Z axes of the clamping mechanism with itself (e.g., alignment of the anvil with the cartridge) on each side of the organ is necessary for proper formation of B-shaped staples.
Alignment difficulties are intensified by the trend toward minimally invasive surgical procedures in which the organ is remotely accessed through small incisions. A trocar or other cannula is inserted into each incision and becomes the access point into the body cavity for surgical devices, including staplers.
Typically, the surgeon inserts at least the end effector of the stapler through the trocar to perform the surgical procedure. By way of example, minimally invasive surgical procedures include a laparoscopic vertical sleeve gastrectomy. Due to this restricted spacial environment, minimally invasive surgical stapling devices must be relatively small compared to open linear surgical staplers. Minimally invasive devices are generally long (e.g., 35 cm to 45 cm) and thin (e.g., 5 mm to 15 mm diameter) devices. This long and thin configuration is necessary to fit through the trocar into the body cavity. The limited size presents a mechanical issue as B-shaped staple formation typically requires a pressure of about 100 psi. Under these pressures, small, less rigid, staplers deform and so prevent proper B-shaped staple formation.
Along the same lines, current devices used in minimally invasive surgical procedures have a fixed hinge at a proximal end. The hinge allows the anvil and cartridge to separate into a V-shaped configuration. Once separated, the surgeon may place the V around the organ and then collapse the V onto the organ. As the length of the anvil and cartridge increase, typically to provide a single, longer staple line across the organ, alignment between the anvil and the cartridge becomes more difficult, and the end effector is more difficult to manipulate through the trocar. Poor alignment is problematic, because with a hinge design, the anvil and/or cartridge at the most distant ends are more likely to be displaced from an ideal alignment due to deflection associated with the forces necessary to compress the tissue. Because of this deflection, the length of current V-shaped staplers for minimally invasive procedures is limited. As a result of this limitation, the anvil and the cartridge are limited in length. Limitations on length are problematic because this may require multiple staple reloads. Each reload may require the surgeon to withdraw the stapler from the trocar and then reinsert and reposition the stapler on the organ. Ultimately, these devices require more surgical time and are more likely to fail to provide consistent B-shaped staples when activated.
One solution to deflection is to provide two points of connection between the anvil and the cartridge instead of a single, hinged connection. That is, the anvil and the cartridge are coupled together at each end. However, this connection has been limited to open surgical procedures in which the surgeon has direct access to each end of the stapler and in which relatively large staplers may be utilized. In open surgery, the surgeon can directly manipulate one or both of the connections by hand. Furthermore, two-pointed connections require that the anvil and the cartridge extend beyond the full dimension of the organ. This requires a large device that, while possibly appropriate for open surgery, is not usable in minimally invasive procedures.
While current staplers are adequate, new devices and methods are needed to address the shortcomings of existing staplers and methods in minimally invasive surgical procedures. More particularly, new minimally invasive staplers and methods are needed that offer improved maneuverability and more uniform pressure application on the tissue, while providing consistent and quality resection lines created during medical procedures, such as during a vertical sleeve gastrectomy.